Base station apparatus and radio communication method

ABSTRACT

Taking into account an optimal reception characteristic of a communication apparatus with variable directivity, the base station apparatus of the present invention has a communication apparatus with variable directivity positively accommodate a communication with a terminal in poor reception conditions, which makes it possible to reduce power of this terminal and reduce interference, thereby increasing the subscriber capacity in the system.

TECHNICAL FIELD

[0001] The present invention relates to a base station apparatus andradio communication method in a digital radio communication system.

BACKGROUND ART

[0002] A conventional radio communication system is explained. FIG. 1 isa schematic view showing a conventional radio communication system usingsector antennas. FIG. 2 is a schematic view showing a conventional radiocommunication system using variable directivities.

[0003] First, the conventional radio communication system using sectorantennas is explained with reference to FIG. 1. For example, basestation 1 carries out communications with three fixed directivitiestoward sector antenna (fixed directivity) A, sector antenna (fixeddirectivity) B and sector antenna (fixed directivity) C. Normally,setting such fixed directivities in different directions is called“sectorization.” Base station 1 communicates with terminal A2 with fixeddirectivity A. Base station 1 further communicates with terminal B3 withfixed directivity B.

[0004] Thus, a radio communication system using many fixed directivitiesimproves its reception characteristic using a diversity technology forincreasing the number of antennas on the base station side. In a mobilecommunication environment in particular, the diversity technologycompensates a drop of reception field intensity due to fading.

[0005] Next, a conventional radio communication system using variabledirectivities is explained with reference to FIG. 2. For example, basestation 1 communicates with terminal A2 with variable directivity A.Base station 1 further communicates with terminal B3 with variabledirectivity B.

[0006] Thus, carrying out communications with a narrow directivityformed for every terminal makes it possible to improve frequencyutilization. This technique is reported in TECHNICAL REPORT OF IEICEA•P96-131, etc. In addition, a system of performing control for everyterminal so that a desired signal is received in optimal conditions andtransmitting using a weighting factor generated at that time isdescribed in ICIEC.Trans.COMMUN., VOL.E77-B, No.5 May, 1994.

[0007] Moreover, a method for performing control for every terminal sothat a desired signal is received in optimal conditions, using theimproved reception quality for a reduction of transmit power on theterminal side and increasing the subscriber capacity of the uplink isdescribed in TECHNICAL REPORT OF IEICE IT96-66 (1997-03). The concept oftransmit power control is reported in TECHNICAL REPORT OF IEICE A•96-155(1997-02).

[0008] However, according to the conventional system, if the size ofsectors is reduced, handover takes place more frequently betweendifferent sectors, which complicates communication control by a basestation interrupting communications. Furthermore, in a CDMAcommunication system, identical signals spread by different spreadingcodes, are sent from a plurality of sectors to a same terminal toprevent the communication from being interrupted during handover. Thisfunction is called “diversity handover.” However, signals directed to asame terminal are sent to a plurality of sectors during diversityhandover, causing a shortage of the communication capacity on thedownlink (communication channel from a base station to a terminal).

[0009] Moreover, in the technique disclosed in ICIEC.Trans.COMMUN.,VOL.E77-B, No.5 May, 1994, reception signal correlation is about 1because a signal is received by an array antenna. In a mobilecommunication environment, this will result in considerabledeterioration in the characteristic when the intensity of a receptionsignal drops due to fading. Therefore, the communication quality needsto be compensated by diversity as in the case where sector antennas areused. However, since array antennas to form variable directivities arelarge and expensive, it is difficult to perform diversity with aplurality of array antennas.

[0010] Moreover, in the technique disclosed in TECHNICAL REPORT OF IEICEIT96-66 (1997-03), a drop of field intensity due to fading in a mobilecommunication environment is compensated by transmit power control onthe terminal side. However, this needs high-speed transmit power controlto follow up the mobile communication environment, requiring anexpensive transmission amplifier for the terminal. Furthermore, sincedeterioration of the reception quality at the base station iscompensated by the terminal, transmit power of the terminal increases,whereas the communication time and wait time are shortened.

[0011] Furthermore, since the conventional base station apparatus doesnot have a configuration that allows the number of terminalsaccommodated by the sector antennas or the number of terminalsaccommodated with variable directivities to be increased as required,the base station needs to be replaced.

DISCLOSURE OF THE INVENTION

[0012] It is an object of the present invention to provide a basestation apparatus and radio communication method, which are easy tocontrol, resistant to fading in a mobile communication environment andcapable of changing the number of terminals accommodated with variabledirectivities.

[0013] A main subject of the present invention is to increase thesubscriber capacity in the system, taking account of a good receptioncharacteristic of a communication apparatus with variable directivities,by having the communication apparatus with variable directivitiespositively accommodate communications with terminals in poor receptionconditions and reducing power of these terminals to reduce interference.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 illustrates a model of a conventional radio communicationsystem;

[0015]FIG. 2 illustrates another model of a conventional radiocommunication system;

[0016]FIG. 3 is a block diagram showing a configuration of a basestation apparatus according to Embodiment 1 of the present invention;

[0017]FIG. 4 illustrates a model of a system according to the embodimentof the present invention;

[0018]FIG. 5 illustrates a relation between a gain and direction in thebase station apparatus according to the embodiment above;

[0019]FIG. 6 is a block diagram showing a directivity formation sectionof the base station apparatus according to the embodiment above;

[0020]FIG. 7 is a block diagram showing a configuration of a basestation apparatus according to Embodiment 2 of the present invention;

[0021]FIG. 8 is a block diagram showing a transmission directivitydetection section of the base station apparatus according to theembodiment above;

[0022]FIG. 9 is a block diagram showing a transmission directivitydetection section of a base station apparatus according to Embodiment 3of the present invention;

[0023]FIG. 10 is a drawing to explain a directivity of the base stationapparatus according to the embodiment above;

[0024]FIG. 11 is a block diagram showing a transmission directivitydetection section of a base station apparatus according to Embodiment 4of the present invention;

[0025]FIG. 12 is a block diagram showing a reception section of the basestation apparatus according to Embodiment 4 of the present invention;

[0026]FIG. 13 is a block diagram showing a reception section of a basestation apparatus according to Embodiment 6 of the present invention;

[0027]FIG. 14 is a block diagram showing a base station apparatusaccording to Embodiment 7 of the present invention;

[0028]FIG. 15 is a block diagram showing a base station apparatusaccording to Embodiment 8 of the present invention;

[0029]FIG. 16 is a block diagram showing a combination section of thebase station apparatus according to Embodiment 4 of the presentinvention;

[0030]FIG. 17 is a block diagram showing a combination section of a basestation apparatus according to Embodiment 5 of the present invention;and

[0031]FIG. 18 is a block diagram showing a base station apparatusaccording to Embodiment 9 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0032] With reference now to the attached drawings, embodiments of thepresent invention are explained in detail below.

EMBODIMENT 1

[0033]FIG. 3 is a block diagram showing a configuration of a basestation apparatus according to Embodiment 1 of the present invention. Inthe base station apparatus shown in FIG. 3, signals received by arrayantenna 101 are subjected to amplification, frequency conversion and A/Dconversion by radio transmission/reception sections 105 a to 105 c.These signals are sent to variable directivity reception section 109 inwhich a plurality of directivities is formed and reception processing iscarried out according to these directivities. Then, of the results ofreception with directivity, the directivity corresponding to the largestreception power of a desired signal is selected and demodulated. Thedemodulation result is sent to switching section 110.

[0034] Signals received by sector antennas 102 to 104 are subjected toamplification, frequency conversion and A/D conversion by radiotransmission/reception sections 106 to 108, respectively and thesesignals are demodulated by reception sections 111 to 113 and thedemodulation results are sent to switching section 110. Switchingsection 110 gathers and outputs the reception signals into a singlesignal line.

[0035] Assignment control section 117 controls assignment of thetransmission signal to array antenna 101 or sector antennas 102 to 104.If the transmission signal is assigned to the sector antennas, thetransmission signal is modulated by one of transmission sections 114 to116, subjected to quadrature modulation, frequency conversion andamplification by one of radio transmission/reception sections 106 to 108and transmitted from one of antennas 102 to 104.

[0036] On the other hand, if the transmission signal is assigned to thearray antenna, the transmission signal is modulated by variabledirectivity transmission section 119, multiplied by a directivityselected by variable directivity reception section 109 and sent to radiotransmission/reception sections 105 a to 105 c. The transmission signalis subjected to quadrature modulation, frequency conversion andamplification by the transmission section and transmitted from arrayantenna 101.

[0037]FIG. 4 is an illustration showing a directivity model in the basestation apparatus according to this embodiment of the present invention(the same applies to the rest of embodiments). Base station 201 carriesout communications with fixed directivities, for example, in threedirections of sector antenna (fixed directivity A) 202, sector antenna(fixed directivity B) 203 and sector antenna (fixed directivity C) 204,and a communication with variable directivity in one direction ofvariable directivity 205. For example, this radio communication systemcarries out a radio communication with terminal 206 using sector antenna202 and a radio communication with terminal 207 using array antenna(variable directivity antenna) 205.

[0038] Then, the operation of the base station apparatus with the aboveconfiguration is explained.

[0039] On the receiving side, signals received from array antenna 101are subjected to amplification, frequency conversion and A/D conversionby radio transmission/reception sections 105 a to 105 c and sent tovariable directivity reception section 109 in which a plurality ofdirectivities are formed.

[0040] The directivity formation method here is described in “AntennaEngineering Handbook” (published by Ohmsha, Oct. 30, 1980) pp.200-205.That is, suppose N antennas simply spaced at regular intervals (d) on astraight line. Directivities can be expressed as shown in expressions(1) to (3). Expression (1) is a deformation of expression 3·3 of thereference above, expression (2) corresponds to expression 3·4 of thereference and expression 3 is a new description. $\begin{matrix}\begin{matrix}{{E(u)} = \quad {\sum\limits_{n = 0}^{N - 1}{I_{n}{\exp \left( {j\quad n\quad u} \right)}}}} \\{= \quad {\sum\limits_{n = 0}^{N - 1}{I_{n}{\exp \left( {{- j}\quad {nkd}\quad \cos \quad \theta} \right)}{\exp \left( {j\quad {nkd}\quad \cos \quad \theta} \right)}}}} \\{= \quad {\sum\limits_{n = 0}^{N - 1}{I_{n}^{\prime}{\exp \left( {j\quad {nkd}\quad \cos \quad \theta} \right)}}}}\end{matrix} & (1)\end{matrix}$

U=kd (cosθ−cosθ₀)   (2)

I _(n) =I _(n)exp(−jnkd cos θ₀)   (3)

[0041] Where In′ denotes a current given to the nth antenna (complexnumber having an amplitude and phase) , k denotes the number of signals,θ₀ denotes a direction in which directivity is directed, and θ denotes avariable to draw directivity. For brevity, suppose In is in-phase andhas a same amplitude, that is, In-1.0. By giving each antennaexp(−jnkd·cosθ₀) it is possible to direct the directivity in the θ₀direction.

[0042] Through such calculations, a plurality of weighting factors isprepared for every direction of arrival and reception with directivityis carried out using these weighting factors. For example, as shown inFIG. 5, a case where weighting factors are prepared to form twodirectivities 301 and 302 is explained. More specifically, an outline ofoperation for reception with directivity is explained using FIG. 6.

[0043] Array antenna reception signals are input to complex processingcircuits 401 and 402. These array antenna reception signals correspondto the signals input from radio transmission/reception signals 105 a to105 c to variable directivity reception section 109. Complex processingcircuit 401 multiplies the array antenna reception signals by theweighting factors generated by weighting factor generator 405 usingexpression (3) above to form directivity 301. That is, one array antennareception signal is multiplied by a weighting factor calculated fromexpression (3) above when n=0, another array antenna reception signal ismultiplied by a weighting factor calculated from expression (3) abovewhen n=1, and the other array antenna reception signal is multiplied bya weighting factor calculated from expression (3) above when n=2. Thesemultiplication results are added up.

[0044] Likewise, complex processing circuit 402 multiplies the arrayantenna reception signals by the weighting factors generated byweighting factor generator 405 using expression (3) above to formdirectivity 302. That is, one array antenna reception signal ismultiplied by a weighting factor calculated from expression (3) abovewhen n=0, another array antenna reception signal is multiplied by aweighting factor calculated from expression (3) above when n=1, and theother array antenna reception signal is multiplied by a weighting factorcalculated from expression (3) above when n=2. These multiplicationresults are added up.

[0045] Then, reception power of the desired signals of respectivecombined signals is measured by level detection sections 403 and 404 andthese measurement results are sent to selection section 406. Selectionsection 406 outputs the combined signal and reception directivity ofgreater reception power of the desired signals. Here, if the desiredsignals have almost the same reception power as the measurement results,selection section 406 selects the one with the greatersignal-to-interference ratio. Furthermore, weighting factors generatedby weighting factor generator 405 are also sent to selection section406. These reception signals correspond to signals sent from variabledirectivity reception section 109 to switching section 110 in FIG. 3 andthe reception directivity corresponds to signals sent from variabledirectivity reception section 109 to variable directivity transmissionsection 119 in FIG. 3.

[0046] On the transmitting side, assignment control section 117 performscontrol of assigning the transmission signal to sector antennas 102 to104 or array antenna 101. When assigned to sector antennas 102 to 104,the transmission signal is modulated by one of transmission sections 114to 116 and subjected to quadrature modulation, frequency conversion andamplification by one of radio transmission/reception sections 106 to 108and sent via one of sector antennas 102 to 104. The signal flow in thiscase is as shown in FIG. 3.

[0047] If array antenna 101 is selected, the transmission signal ismodulated by variable directivity transmission section 119, subjected toquadrature modulation, frequency conversion and amplification by radiotransmission/reception sections 105 a to 105 c and sent from arrayantenna 101.

[0048] Then, the assignment method in the base station apparatus aboveis explained. Assignment control section 117 determines whether toassign the sector antennas or array antenna as the reception antennaaccording to the following method:

[0049] First, a first assignment method is explained.

[0050] Terminals with small interference with other terminals such asterminals carrying out voice communication and low-speed datacommunication are accommodated by the sector antennas (with fixeddirectivity), while terminals with large interference with otherterminals such as terminals carrying out high-speed data areaccommodated by the array antenna (with variable directivity). Inparticular, when the sector antennas are assigned as the receptionantennas, since the sector antennas are configured by a plurality ofsectors, it is preferable to assign them to directions in which theuplink control channel is received with the best quality.

[0051] When controlling the assignment of antennas from the transmissionsignal, information on the information speed in the transmission signalis sent to assignment control section 117. Assignment control section117 controls switching sections 110 and 118 according to the firstassignment method.

[0052] On the other hand, when controlling the assignment of antennasfrom the reception signal, information on the information speed (datarate) in the reception signal is sent to assignment control section 117.Assignment control section 117 controls switching sections 110 and 118according to the first assignment method.

[0053] Here, the data rate of the reception signal is measured andassignment processing is performed considering that the higher the datarate, the greater the interference with other terminals and the lowerthe data rate, the smaller the interference with other terminals.However, it is also possible to find the level of interference withother terminals using a different method and carry out assignmentprocessing based on the result.

[0054] Doing so, it is possible to narrow the transmission directivityfor terminals with a large amount of interference, narrow the spatialarea that gives interference and thus prevent deterioration of thereception quality of other terminals. Furthermore, using the arrayantenna with variable directivity, it is not necessary to transmit to aplurality of sectors for diversity handover between fixed CDMA sectorsand it is possible to prevent the subscriber capacity from being reduceddue to diversity handover. Moreover, in a CDMA communication if acommunication is carried out at high speed, it is necessary to increasetransmit power, but it is possible to narrow the reception directivityfor terminals with large interference and improve the reception qualityof terminals communicating high-speed data, thereby allowing thecommunication range to be broadened.

[0055] Then, the second assignment method is explained.

[0056] Terminals with small interference with other terminals such asterminals carrying out voice communication and low-speed datacommunication are accommodated by the sector antennas, while terminalswith poor reception quality are accommodated by the array antenna. Inparticular, when the sector antennas are assigned as the receptionantennas, since the sector antennas are configured by a plurality ofantennas, it is preferable to assign them to directions in which theuplink control channel is received with the best quality.

[0057] When controlling the assignment of antennas from the transmissionsignal, information on the information speed in the transmission signalis sent to assignment control section 117. Assignment control section117 controls switching sections 110 and 118 according to the secondassignment method.

[0058] On the other hand, when controlling the assignment of antennasfrom the reception signal, information on the information speed in thereception signal is sent to assignment control section 117. Here, theterminal apparatus is provided with a section for broadcasting theaverage reception level of a perch channel, which is a broadcast channelto determine whether the terminal apparatus is far from the base stationor not. The terminal apparatus measures the average reception level ofthe perch channel. Then, the terminal apparatus broadcasts this averagereception level of the perch channel to the base station over theuplink. The base station decodes the information of the averagereception level, which is the reception quality, and sends theinformation on this average reception level to assignment controlsection 117. Assignment control section 117 controls switching sections110 and 118 according to the second assignment method.

[0059] Here, the reception quality is measured using the perch channelaverage reception level, but it is also possible to measure thereception quality using a frame error rate based on a CRC bit errordetermination or signal-to-interference ratio or other qualityparameters.

[0060] Doing so, it is possible to improve the quality of communicationswith terminals with poor communication quality preferentially.

[0061] Then, the third assignment method is explained.

[0062] Terminals with small interference with other terminals such asterminals carrying out voice communication and low-speed datacommunication are accommodated by the sector antennas, while, ofterminals with large interference with other terminals such ashigh-speed data communication, terminals located far are accommodated bythe array antenna preferentially. In particular, this is effective whenthe number of terminals carrying out a high-speed communication exceedsthe number of communication apparatuses with provided variabledirectivities. Furthermore, when the sector antennas are assigned, sincethe sector antennas are configured by a plurality of sectors, it ispreferable to assign them to directions in which the uplink controlchannel is received with the best quality.

[0063] When controlling the assignment of antennas from the transmissionsignal, information on the information speed in the transmission signalis sent to assignment control section 117. Assignment control section117 controls switching sections 110 and 118 according to the thirdassignment method.

[0064] On the other hand, when controlling the assignment of antennasfrom the reception signal, information on the information speed in thereception signal is sent to assignment control section 117. Here, theterminal apparatus is provided with, for example, a section forbroadcasting the average reception level of a perch channel, which is abroadcast channel to determine whether the terminal apparatus is farfrom the base station or not. The terminal apparatus broadcasts thisaverage reception level of the perch channel to the base station overthe uplink. The base station decodes the information of the averagereception level, which is the reception quality, and sends theinformation of this average reception level to assignment controlsection 117. Assignment control section 117 controls switching sections110 and 118 according to the third assignment method.

[0065] In this case, if no transmit power control is performed, it isdetermined by the level of the average reception level whether theterminal is located far or not. That is, a terminal whose averagereception level is low is determined as a far terminal and this terminalis preferentially accommodated by the array antenna. On the other handif transmit power control is performed, the average reception level isconstant within a range in which transmit power control is possible, andtherefore it is determined whether the-terminal is located far or not bythe average reception level within a range in which transmit powercontrol is impossible in the same way as shown above.

[0066] In this way, terminals with poorer communication quality areaccommodated by the provided communication apparatus with variabledirectivity. As a result, it is possible to preferentially improve thequality of communication with terminals with poor communication quality.

[0067] Then, the fourth assignment method is explained.

[0068] Terminals with small interference with other terminals such asterminals carrying out voice communication and low-speed datacommunication are accommodated by the sector antennas, while, ofterminals carrying out high-speed data communication, terminals carryingout faster data communication are accommodated by the array antennapreferentially. In particular, this is effective when the number ofterminals carrying out a high-speed data communication exceeds thenumber of provided communication apparatuses with variable directivity.Furthermore, when terminals are assigned to the sector antennas, sincethe sector antennas are configured by a plurality of sectors, it ispreferable to assign them to directions in which the uplink controlchannel is received with the best quality.

[0069] When controlling the assignment of antennas from the transmissionsignal, information on the information speed in the transmission signalis sent to assignment control section 117. Assignment control section117 controls switching sections 110 and 118 according to the fourthassignment method. That is, communication of a terminal carrying out acommunication at a higher data rate is preferentially accommodated bythe array antenna.

[0070] On the other hand, when controlling the assignment of antennasfrom the reception signal, information on the information speed in thereception signal is sent to assignment control section 117. Assignmentcontrol section 117 controls switching sections 110 and 118 according tothe fourth assignment method.

[0071] Using such an assignment method, terminals carrying out fasterdata communication, that is, terminals with a larger amount ofinterference are accommodated by the provided communication terminalwith variable directivity. As a result, it is possible to narrowtransmission directivity toward terminals with a large amount ofinterference, narrow a spatial area that gives interference and thusprevent deterioration of reception quality of other terminals.

[0072] Furthermore, because of diversity handover between CDMA sectors,it is not necessary to send data to a plurality of sector antennas andit is possible to prevent the subscriber capacity from being reduced dueto diversity handover. Furthermore, in the CDMA communication, ifcommunication is carried out at high speed, it is necessary to increasetransmit power, but it is possible to narrow the reception directivitytoward terminals with large interference and improve the receptionquality of terminals communicating high-speed data, thereby broadeningthe communication range. This also makes control simpler and makes thesystem more resistant to fading in a mobile communication environment.

[0073] In W-CDMA, a transmission rate maybe broadcast from the networkside or a variable rate may be used. In either case, the rate isidentified and the assignment process above is carried out based on theidentification result. That is, the transmission rate is identified byreceiving information of the rate when broadcast from the network sideand by measuring the rate in the case of a variable rate.

EMBODIMENT 2

[0074]FIG. 7 is a block diagram showing a configuration of a basestation apparatus according to Embodiment 2 of the present invention.The parts in FIG. 7 identical to those in FIG. 3 are assigned the samecodes as those in FIG. 3 and their detailed explanations are omitted.

[0075] The base station apparatus shown in FIG. 7 is provided withtransmission directivity detection section 501 that detects transmissiondirectivity based on the reception signal from radiotransmission/reception sections 105 a to 105 c of array antenna 101.Information on the transmission directivity detected by thistransmission directivity detection section 501 is sent to variabledirectivity transmission section 119 in which transmission directivitiesare changed.

[0076] The operation of the base station apparatus according toEmbodiment 2 of the present invention is explained using FIG. 7.

[0077] Signals received by array antenna 101 are subjected toamplification, frequency conversion and A/D conversion by radiotransmission/reception sections 105 a to 105 c and sent to variabledirectivity reception section 109. Here, variable directivity receptionsection 109 is explained using FIG. 8. This variable directivityreception section is implemented by an adaptive array antenna. Thisadaptive array antenna is described in “Waveform Equalization Technologyfor Digital Mobile Communications” (published by Triceps Corporation onJun. 1, 1996, ISBN4-88657-801-2), etc.

[0078] For example, if adaptive array antenna processing is carried outso as to extract a desired signal, directivity is directed to thedesired signal and a portion with a small gain (called “null”) isproduced for an unnecessary signal (a signal identical to the desiredsignal, but arrives at a different time because it travels through adifferent propagation path, or signal from another transmitter). Anexample of this directivity is shown in FIG. 10.

[0079] In variable directivity reception section 109 shown in FIG. 8,the signals received by array antenna are sent to weighting factorcalculation section 604 in which weighting factors are calculated. Theseweighting factors are subjected to complex multiplication with the arrayantenna reception signals by complex multipliers 601 to 603. Thesemultiplication results are added up by adding section 605. This additionresult becomes a reception signal. This corresponds to the output ofvariable directivity reception section 109.

[0080] On the other hand, differential circuit 606 calculates adifference between the addition result and a reference signal and thisdifference is sent to weighting factor calculation section 604 as anerror signal. Weighting factor calculation section 604 updates weightingfactors based on the error signal.

[0081] On the other hand, a signal received by sector antenna 102 issubjected to amplification, frequency conversion and A/D conversion byradio transmission/reception section 106, demodulated by receptionsection 111 and the demodulation result is sent to switching section110. A signal received by sector antenna 103 is subjected toamplification, frequency conversion and A/D conversion by radiotransmission/reception section 107, demodulated by reception section 112and the demodulation result is sent to switching section 110. A signalreceived by sector antenna 104 is subjected to amplification, frequencyconversion and A/D conversion by radio transmission/reception section108, demodulated by reception section 113 and the demodulation result issent to switching section 110. Switching section 110 gathers allreception signals together into one and outputs.

[0082] On the transmitting side, assignment control section 117 performscontrol of assigning the transmission signal to sector antennas 102 to104 or array antenna 101. When assigned to sector antennas 102 to 104,the transmission signal is modulated by one of transmission sections 114to 116, subjected to quadrature modulation, frequency conversion andamplification by one of radio transmission/reception sections 106 to 108and transmitted by one of sector antennas 102 to 104. The signal flow inthis case is as shown in FIG. 7.

[0083] If array antenna 101 is selected, the transmission signal ismodulated by variable directivity transmission section 119. Furthermore,the directivity information selected by transmission directivitydetection section 501 is sent to variable directivity transmissionsection 119 and directivity is changed based on this selecteddirectivity information. The transmission signal is subjected toquadrature modulation, frequency conversion and amplification by radiotransmission/reception sections 105 a to 105 c and transmitted fromarray antenna 101.

[0084] Here, the method of assignment of sector antennas 102 to 104 andarray antenna 101 is the same as that of Embodiment 1.

[0085] Then, transmission directivity detection section 501 is explainedusing FIG. 9. Transmission directivity is detected by receiving signalswith a plurality of directivities, selecting the directivity withmaximum reception power of a desired signal from those directivities andthis directivity is used as the directivity for downlink transmission.The method of forming directivity is the same as that of Embodiment 1.

[0086] Thus, transmission directivity detection section 501 prepares aplurality of weighting factors for every direction of arrival andcarries out reception with directivity. For example, transmissiondirectivity detection section 501 prepares weighting factors to form twodirectivities as shown in FIG. 5.

[0087] In transmission directivity detection section 501, the arrayantenna reception signals are input to complex processing sections 701and 702. These array antenna reception signals correspond to the outputsof radio transmission/reception sections 105 a to 105 c.

[0088] Complex processing section 701 multiplies the array antennareception signals by a weighting factor generated by weighting factorgenerator 705 using aforementioned expression (3) to form directivity301. That is, the weighting factor calculated from aforementionedexpression (3) with n=0 is multiplied on the reception signal of onearray antenna, the weighting factor calculated from aforementionedexpression (3) with n=1 is multiplied on the reception signal of anotherarray antenna and the weighting factor calculated from aforementionedexpression (3) with n=2 is multiplied on the reception signal of theother array antenna. These multiplication results are added up.

[0089] Likewise, complex processing section 702 multiplies the arrayantenna reception signals by the weighting factor generated by weightingfactor generator 705 using aforementioned expression (3) to formdirectivity 302. That is, the weighting factor calculated fromaforementioned expression (3) with n=0 is multiplied on the receptionsignal of one array antenna, the weighting factor calculated fromaforementioned expression (3) with n=1 is multiplied on the receptionsignal of another array antenna and the weighting factor calculated fromaforementioned expression (3) with n=2 is multiplied on the receptionsignal of the other array antenna. These multiplication results areadded up.

[0090] Then, level detection sections 703 and 704 measure the desiredsignal reception power of their respective combined signals and send themeasurement results to selection section 706. Selection section 706selects and outputs the reception directivity corresponding to thegreater desired signal reception power. If these combined signals havealmost same desired signal reception power, the one with a greatersignal-to-interference ratio is selected. This reception signalcorresponds to the signal sent from variable directivity receptionsignal 109 to switching section 110.

[0091] This embodiment explains the case where an adaptive array antennais used for the base station apparatus with the configuration shown inFIG. 7, but the same effect will also be obtained in a case where anadaptive array antenna is used for the base station apparatus with theconfiguration shown in FIG. 3.

EMBODIMENT 3

[0092] This embodiment explains a case where a technique of estimatingthe direction of arrival of a reception signal is used to detecttransmission directivity. The configuration of the base stationapparatus in this embodiment is the same as that shown in FIG. 7.Therefore, operations other than detection of transmission directivityare the same as those in Embodiment 2 and so their detailed explanationsare omitted.

[0093] The transmission directivity detection section in this embodimentcomprises direction of arrival estimator 901 and directivity formationsection 902 as shown in FIG. 11. That is, transmission directivity isgenerated by direction of arrival estimator 901 estimating the directionof arrival of a reception signal and calculating the directivity basedon the direction of arrival. More specifically, directivity formationsection 902 assigns the direction detected by direction of arrivalestimator 901 to θ₀ in aforementioned expression (3) and calculates aweighting factor necessary to form directivity.

[0094] The direction of arrival estimation technique is described in“Introduction to Adaptive Signal Processing Technology Using ArrayAntenna and High Resolution Direction of Arrival Estimation” publishedby the Institute of Electronics, Information and Communication Engineerspp.62-76 (Oct. 30, 1997), etc.

[0095] The following effect is obtained from Embodiments 1 to 3 above.

[0096] The direction of arrival estimation technique can narrowtransmission directivity toward terminals with large interference,narrow the spatial area that gives interference and preventdeterioration of reception quality of other terminals. Furthermore,diversity handover between CDMA fixed sectors further eliminates theneed to transmit to a plurality of sectors, preventing the subscribercapacity from being reduced by diversity handover. In a CDMAcommunication, if a communication is carried out at high speed, it isnecessary to increase transmit power but it possible to narrow thereception directivity toward terminals with large interference andimprove the reception quality of terminals communicating high-speeddata, thereby broadening the communication range.

[0097] Furthermore, the direction of arrival estimation technique canimprove the quality of communication with terminals with poorcommunication quality preferentially. Furthermore, all communicationapparatuses with variable directivity prepared as apparatusesaccommodate terminals with poorer communication quality. Therefore, itis possible to improve the quality of communication with terminals withpoor communication quality preferentially.

[0098] Furthermore, all communication apparatuses with variabledirectivity prepared as apparatuses accommodate terminals carrying outfaster data communication, that is, terminals with a greater amount ofinterference. This makes it possible to narrow transmission directivitytoward terminals with greater interference, narrow the spatial area thatgives interference and prevent deterioration of reception quality ofother terminals. Furthermore, diversity handover between CDMA fixedsectors further eliminates the need to transmit data to a plurality ofsectors, preventing the subscriber capacity from being reduced bydiversity handover.

EMBODIMENT 4

[0099] The base station apparatus in this embodiment is a case wheresignals received by sector antennas 102 to 104 and array antenna 101 arecombined. FIG. 12 is a block diagram showing a configuration of areception section of the base station apparatus according to Embodiment4 of the present invention. The base station apparatus of thisembodiment applies an adaptive array antenna to the base stationapparatus with the configuration shown in FIG. 3. Therefore, the basestation apparatus of this embodiment is the same as the embodiment aboveexcept for the section that combines reception signals, and so theirdetailed explanations are omitted.

[0100] The base station apparatus of this embodiment combines signalsreceived by sector antennas 102 to 104 and array antenna 101 bycombination section 1001. This combination section 1001 has aconfiguration shown in FIG. 16. In combination section 1001, envelopedetection section 1401 detects the envelope of the output of variabledirectivity reception section 109 and phase detection section 1402detects the phase of the output of variable directivity receptionsection 109. Phase rotation section 1403 corrects the phase of thereception signal based on the phase information detected by phasedetection section 1402. Furthermore, the reception signal is amplifiedby amplifier 1404 based on the information of the envelope detected byenvelope detection section 1401.

[0101] Likewise, also for reception signals of sector antennas 102 to104, envelope detection section 1405 and phase detection section 1406detect the envelope and phase, phase rotation section 1407 carries outphase correction and amplifier 1408 amplifies their respective receptionsignals (FIG. 16 only describes a portion corresponding to one sectorantenna). Then, adder 1409 adds up the results corresponding to arrayantenna 101 and sector antennas 102 to 104.

EMBODIMENT 5

[0102] This embodiment explains another example of combination of theoutputs of array antenna 101 and sector antennas 102 to 104. Theconfiguration and operation of other than the combination section arethe same as those in Embodiment 4.

[0103]FIG. 17 shows a configuration of the combination section of thebase station apparatus according to this embodiment. The combinationsection sends the output of variable directivity reception section 109and the reception signals of sector antennas 102 to 104 to weightingfactor calculation section 1505 in which weighting factors arecalculated, and complex multipliers 1501 to 1504 multiply the output ofvariable directivity reception section 109 and the reception signals ofsector antennas 102 to 104 by those weighting factors and adding section1506 adds up their respective multiplication results. This additionresult becomes the reception signal.

[0104] Differential section 1507 calculates a difference between areference signal and the combined reception signal and sends the resultto weighting factor calculation section 1505 as an error signal.Weighting coefficient calculation section 1505 updates weighting factorsusing array antenna reception signals and error signal

EMBODIMENT 6

[0105] This embodiment explains another example of combination of theoutputs of array antenna 101 and sector antennas 102 to 104. Theconfiguration and operation of other than the combination section arethe same as those in Embodiment 4.

[0106] When sector antennas(fixed directivity) are placed in differentdirections as shown in FIG. 4, the reception quality of a desired signalvaries depending on the direction. Thus, it is possible to limit signalsto be combined beforehand. The reception section of the base stationapparatus according to this embodiment has a configuration as shown inFIG. 13. Such a configuration can limit signals to be combinedbeforehand.

[0107] In this reception section, reception signals of sector antennas102 to 104 are input to level detection sections 1101 to 1103 in whichreception power is measured and the measurement results are sent toselection section 1104. Selection section 1104 selects signal whoselevel measured value exceeds a predetermined threshold and outputs thesignal to combination section 1105. Combination section 1105 combinesthese signals according to the method explained in Embodiment 4. If thereception signals of the sector antennas include a desired signal andinterference signal, the reception section measures reception power ofthe desired signal and sends the measurement result to selection section1104.

[0108] The embodiment above explains the case where the combinationmethod of Embodiment 4 is applied, but the same effect can be obtainedalso when the combination method of Embodiment 5 is applied.

[0109] Embodiments 4 to 6 above can compensate a drop of the level ofreception signals due to fading by using the reception signals of thesector antennas without using a plurality of expensive array antennas.

EMBODIMENT 7

[0110] This embodiment explains a case where signals are received usingarray antenna 101 and sector antennas 102 to 104 and transmitted onlyfrom array antenna 101. FIG. 14 is a block diagram showing aconfiguration of the base station apparatus according to Embodiment 7 ofthe present invention.

[0111] In this base station apparatus, array antenna 101 performs arrayantenna reception. Reception signals are subjected to amplification,frequency conversion and A/D conversion by radio transmission/receptionsections 105 a to 105 c and sent to variable directivity receptionsection 109. Variable directivity reception section 109 performsprocessing using one of the methods explained in Embodiments 1 to 3.

[0112] Signals received by sector antennas 102 to 104 are subjected toamplification, frequency conversion and A/D conversion by radiotransmission/reception sections 106 to 108 and sent to combinationsection 1001. Combination section 1001 performs combination using one ofthe methods explained in Embodiments 4 to 6. This combination result issent to transmit power control section 1201.

[0113] Transmit power control section 1201 measures the receptionquality of the combined signal. If this measurement result is equal toor greater than a predetermined threshold, transmit power controlsection 1201 sends such a control signal that reduces transmit power ofa terminal apparatus, which is the other end of communication, to framecomposition section 1202. If this measurement result is smaller than apredetermined threshold, transmit power control section 1201 sends sucha control signal that increases transmit power of the terminal apparatusto frame composition section 1202.

[0114] There are methods of measuring the reception quality such assignal-to-interference ratio and block error rate that decodes CRC(Cyclic Redundancy Check) embedded in a reception signal, etc.

[0115] Then, frame composition section 1202 assigns the transmissionsignal and transmit power control signal to a transmit frame format andsends this transmission signal to variable directivity transmissionsection 119. Variable directivity transmission section 119 multipliesthe transmission signal by a weighting factor according to one of themethods shown in Embodiments 1 to 3, sends this transmission signal toradio transmission/reception sections 105 a to 105 c of array antenna101, carries out quadrature modulation, frequency conversion andamplification, and transmits from array antenna 101.

EMBODIMENT 8

[0116] This embodiment explains a case where signals are received usingarray antenna 101 and sector antennas 102 to 104 and transmitted onlyfrom sector antennas 102 to 104. FIG. 15 is a block diagram showing aconfiguration of the base station apparatus according to Embodiment 8 ofthe present invention.

[0117] In this base station apparatus, array antenna 101 performs arrayantenna reception. Reception signals are subjected to amplification,frequency conversion and A/D conversion by radio transmission/receptionsections 105 a to 105 c and sent to variable directivity receptionsection 109. Variable directivity reception section 109 performsprocessing using one of the methods explained in Embodiments 1 to 3.

[0118] Signals received by sector antennas 102 to 104 are subjected toamplification, frequency conversion and A/D conversion by radiotransmission/reception sections 106 to 108 and sent to combinationsection 1001. Combination section 1001 performs combination using one ofthe methods explained in Embodiments 4 to 6. This combination result issent to transmit power control section 1201.

[0119] Transmit power control section 1201 measures the receptionquality of the combined signal. If this measurement result is equal toor greater than a predetermined threshold, transmit power controlsection 1201 sends such a control signal that reduces transmit power ofthe terminal apparatus, which is the other end of communication, toframe composition section 1202. If this measurement result is lower thanthe predetermined threshold, transmit power control section 1201 sendssuch a control signal that increases transmit power of the terminalapparatus to frame composition section 1202.

[0120] There are methods of measuring the reception quality such as asignal-to-interference ratio and block error rate that decodes CRC(Cyclic Redundancy Check) embedded in a reception signal, etc.

[0121] Then, frame composition section 1202 assigns the transmissionsignal and transmit power control signal to a transmit frame format. Onthe other hand, the signal combined by combination section 1001 is sentto assignment control section 117, and assignment control section 117assigns the sector antenna corresponding to the maximum reception levelcalculated by combination section 1001 to a transmission antenna. Thisassignment information is sent to switching section 118 and the sectorantennas are switched based on the assignment information. Thetransmission signal is modulated by the assigned transmission section,subjected to quadrature modulation, frequency conversion andamplification and transmitted from the antenna.

[0122] Embodiments 7 and 8 above display the following effects:

[0123] It is possible to compensate drops in the reception signal leveldue to fading by using the reception signals of the sector antennasinstead of using a plurality of expensive array antennas.

[0124] Furthermore, since drops in the reception signal level due tofading are not compensated by means of transmit power control ofterminals, it is possible to reduce the response speed of transmit powercontrol of the transmission amplifier of the terminal and reducetransmit power of the terminal.

[0125] Furthermore, it is also possible to expand the system accordingto the number of terminals accommodated by expensivetransmission/reception apparatuses with variable directivity.

EMBODIMENT 9

[0126] The variable directivity reception section and variabledirectivity transmission section are expensive because they carry outcomplicated calculations at high speed. Therefore, this embodimentadopts such a configuration of a base station apparatus that has acommon radio transmission/reception section, expands the variabledirectivity reception section and variable directivity transmissionsection making it possible to add the number of terminals accommodatedwith variable directivities.

[0127]FIG. 18 is a block diagram showing a configuration of the basestation apparatus according to Embodiment 9 of the present invention.This embodiment explains a case where one array antenna for variabledirectivities made up of N antennas and M sector antennas are provided.Furthermore, this embodiment is provided with q variable directivitytransmission/reception sections and p sector antennatransmission/reception sections. Then, suppose the maximum number ofterminals accommodated by array antennas is P and the maximum number ofterminals accommodated by sector antennas is Q.

[0128] In this base station apparatus, array antenna 1601 performs arrayantenna reception. Reception signals are subjected to amplification,frequency conversion and A/D conversion by radio transmission/receptionsections 1605 a to 1605 c and sent to variable directivity receptionsections 1611 a and 1611 b. At this time, array antenna radiotransmission/reception sections 1605 a to 1605 c are each provided witha section that outputs baseband or IF (intermediate frequency) digitalsignals corresponding to the maximum number (Q) of variable directivitytransmission/reception sections mounted and this output is output todistribution section 1609.

[0129] Distribution section 1609 is provided with an output section to amaximum of Q variable directivity transmission/reception sections 1611.The base station apparatus provides communication services by mounting anecessary number of variable directivity transmission/reception sections(building block system). Variable directivity reception sections 1611perform reception and transmission according to one of the methodsexplained in Embodiments 1 to 8.

[0130] On the other hand, signals received by sector antennas 1602 to1604 are subjected to amplification, frequency conversion and A/Dconversion by radio transmission/reception sections 1606 to 1608,respectively and sent to distribution section 1610. At this time, radiotransmission/reception sections 1606 to 1608 of sector antennas 1602 to1604 are each provided with a section that outputs baseband or IFdigital signals corresponding to the maximum number (P) of sectorantenna transmission/reception sections 1612 a to 1612 c mounted andthis output is output to distribution section 1610.

[0131] Distribution section 1610 is provided with an output section to amaximum of P sector antenna transmission/reception sections 1612. Thebase station apparatus provides communication services by mounting anecessary number of sector antenna transmission/reception sections 1612.Variable directivity reception sections 1612 perform reception andtransmission according to one of the methods explained in Embodiments 1to 8.

[0132] Embodiment 9 above measures the reception quality of a combinedsignal, performs transmit power control based on this result andcontrols assignment of sector antennas and array antenna, thus making itpossible to minimize transmit power of each terminal and decreaseinterference, thereby increasing the subscriber capacity.

[0133] As described above, taking into account an optimal receptioncharacteristic of a communication apparatus with variable directivity,the base station apparatus and radio communication method of the presentinvention have a communication apparatus with variable directivitiespositively accommodate communications with terminals with poor receptionconditions, making it possible to reduce power of these terminals,reduce interference and increase the subscriber capacity in the system.Furthermore, the present invention can simplify control, make the systemresistant to fading in a mobile communication environment and change thenumber of terminals accommodated with variable directivities.

[0134] This application is based on the Japanese Patent ApplicationNo.HEI 10-285642 filed on Oct. 7, 1998, entire content of which isexpressly incorporated by reference herein.

[0135] Industrial Applicability

[0136] The present invention is applicable to a base station apparatusin a digital radio communication system.

What is claimed is:
 1. A base station apparatus comprising: at least onefirst communication means for carrying out a communication with fixeddirectivity; at least one second communication means for carrying out acommunication with variable directivity; and assigning means forassigning communications to said first and second communication meansaccording to communication conditions.
 2. The base station apparatusaccording to claim 1, wherein assigning means assigns a communicationwith small interference with other terminals to said first communicationmeans and a communication with large interference with other terminalsto said second communication means.
 3. The base station apparatusaccording to claim 1, further comprising rate identifying means formeasuring a data rate of the reception signal, wherein said assigningmeans carries out assignment processing based on the data rateinformation from said rate identifying means.
 4. The base stationapparatus according to claim 3, wherein said assigning means assigns acommunication at a relatively low data rate to said first communicationmeans and a communication at a relatively high data rate to said secondcommunication means.
 5. The base station apparatus according to claim 1,further comprising quality measuring means for measuring the quality ofthe reception signal, wherein said assigning means carries outassignment processing based on the measurement result from said qualitymeasuring means.
 6. The base station apparatus according to claim 5,wherein said assigning means assigns a communication with relativelypoor quality to said second communication means.
 7. The base stationapparatus according to claim 1, further comprising rate identifyingmeans for measuring a data rate of the reception signal, wherein, whenthe number of terminals carrying out at a relatively high data rate isgreater than the number of said second communication means, saidassigning means preferentially assigns a communication with terminalslocated far among said terminals to said second communication means. 8.The base station apparatus according to claim 7, further comprising:quality measuring means for measuring the quality of the receptionsignal; and determining means for determining said far terminals basedon the measurement result from said quality measuring means.
 9. The basestation apparatus according to claim 1, further comprising rateidentifying means for measuring a data rate of the reception signal,wherein, when the number of terminals carrying out at a relatively highdata rate is greater than the number of said second communication means,said assigning means preferentially assigns a communication withterminals carrying out communications at higher data rate among saidterminals to said second communication means.
 10. A communicationterminal apparatus carrying out a radio communication with a basestation apparatus, said base station apparatus comprising: at least onefirst communication means for carrying out a communication with fixeddirectivity; at least one second communication means for carrying out acommunication with variable directivity; and assigning means forassigning communications to said first and second communication meansaccording to communication conditions.
 11. A radio communication methodcomprising the steps of: measuring a data rate of a reception signal;assigning communications to at least one first communication means forcarrying out a communication with fixed directivity based on themeasured data rate information and at least one second communicationmeans for carrying out a communication with variable directivity. 12.The radio communication method according to claim 13, which assigns acommunication at a relatively low data rate to said first communicationmeans and a communication at a relatively high data rate to said secondcommunication means.